Montmorillonite clay catalysts for the production of phosphonitrilic chloride

ABSTRACT

A process for producing polymeric phosphonitrilic chlorides by reacting phosphorus pentachloride with ammonium chloride in the presence of acid-treated Montmorillonite clay catalyst.

United States Patent 1 Hardy, Sr. 51 Mar. 4, 1975 1 MONTMORILLONITE CLAYCATALYSTS 3,179,489 4/1965 Becke 423/300 FO H PRODUCTION OF 3.3653471/1968 Lund 252/450 X 3,379,510 4/1968 .luszka 423/300 PHOSPHONITRILICCHLORIDE 3.407.047 10/1968 Paddock at 111.... 423/302 [75] Inventor:Donald Hardy, Sr., Yardley, Pa. 3,575,693 4/1971 Emsley et a1. 423/3003,677,720 7 1972 Ma (1 t'l 1 423 300 1 1 Assigneei FMC Corporation, NewYork, 3,691,099 9/1972 You; 252/450 [22] Filed: May 25, 1973 PrimarrE.\'am1'ner-Oscar R. Vertiz A 1. N 64 [21] pp 0 ,057 AssistantExaminer-Brian E. Hearn [52] U.S. Cl. 423/300, 423/302 [51] Int. Cl Colb25/10 [57] ABSTRACT {58] Field of Search 423/300, 302; 203/6, 8,

703/41. 757/450 A process for producing polymeric phosphonltrlllcchlorides by reacting phosphorus pentachloride with U6] References Citedammonium chloride in the presence of acid-treated UNITED STATES PATENTSMontmorlllomte clay catalyst.

3,029.78} 4/1962 Suwycr ct 211. 252/450 X 4 Claims, N0 DrawingsMONTMORILLONITE CLAY CATALYSTS FOR THE PRODUCTION OF PHOSPHONITRILICCHLORIDE This invention relates to an improved process for themanufacture of phosphonitrilic chlorides by catalyzing the reaction ofammonium chloride with phosphorus pentachloride to producephosphonitrilic chlorides containing substantial amounts of trimeric andtetrameric cyclic phosphonitrilic chlorides.

Phosphazenes are ring or chain compounds which contain alternatingphosphorus and nitrogen atoms in the skeleton, with two substituents oneach phosphorus atoms. Phosphonitrilic chlorides are phosphazenes inwhich at least one substituent is chlorine. Cyclic trimers areconventionally called cyclotriphosphazenes; cyclic tetramers arecyclotetraphosphazenes and high polymers are called polyphosphazenes.Hexachlorocyclotriphosphazene, (PNCl is a key intermediate in thesynthesis of many phosphazene derivatives. This product is manufacturedon a commercial scale in the United States, United Kingdom, and Germany.

The synthesis of phosphazenes involves the reaction of phosphoruspentachloride with ammonium chloride in a solvent such astetrachloroethane or chlorobenzene. The products of this reactioninclude the cyclic trimer and tetramer, polymeric cyclic phosphazenesand a series of polymeric linear species which are endcapped," forexample, by the elements of phosphorus pentachloride or l-lCl. Underfavorable conditions, the trimer and tetramer may constitute as much as90% of the reaction products. It is well known in the art that thereaction comprising heating phosphorus pentachloride and ammoniumchloride in a solvent such as tetrachloroethane and monochlorobenzene atreflux temperatures is catalyzed by anhydrous metallic salts which formcoordination complexes with ammonia. Such use of aluminum chloride,magnesium chloride, zinc chloride and the like is described in U.S. Pat.No. 3,407,047 issued to Paddock et al Oct. 22, 1968, and US. Pat. No.3,462,247 issued to Paddock et al Aug. 19, 1969. it is also well knownthat different catalysts have different effects on reactions, and it isalways desirable to find new catalysts to catalyze the reaction ofammonium chloride with phosphorus pentachloride.

In accordance with the present invention, there is provided a process inwhich an acid-treated Montmorillonite clay is the catalyst used in thepreparation of phosphonitrilic chloride by the reaction of ammoniumchloride with phosphorus pentachloride in an inert solvent. Since U.S.Pat. Nos. 3,407,047 and 3,462,247 to Paddock and Searle emphasize theuse of anhydrous metallic salts capable of forming coordination complexes with ammonium, it is surprising that acid-treated Montmorilloniteclays, which are hydrated salt mixtures, would be suitable catalysts forthe reaction of phosphorus pentachloride with ammonium chloride in aninert solvent.

Fine particle size ammonium chloride (5 to microns in size) or ammoniagas may be used as the nitrogen source. Fine particle size ammoniumchloride or ammonia do not require the presence of the catalyst to reactwith phosphorus pentachloride at suitable reaction rates in producingphosphonitrilic chlorides. It is not always desirable to use ammoniagas, and the fine particle size ammonium chloride (5 to 15 microns insize) is difficult to produce. The cost of preparing the fine particlesize ammonium chloride makes it very desirable to use commerical gradeammonium chloride having a mesh size greater than 200 (US. StandardSieve Series ASTM E-l 1-61); generally, 60 to 200 mesh material is usedin commercial processes. Ammonium chloride having mesh sizes larger than60 is not generally used because of the long reaction times required.

The reactant phosphorus pentachloride is prepared by the conventionalprocess of the chlorination of phosphorus trichloride in a nonaqueoussolvent. The small amounts of nonreacted phosphorus trichloride orpossibly phosphorus oxychloride are not harmful to the main reaction.

Simply heating mixtures of ammonium chloride and phosphoruspentachloride produces phosphonitrilic chloride and large amounts ofgenerally undesired oily polymers. The reaction is, therefore, generallycarried out by the controlled addition of phosphorus pentachloride to astirred suspension of ammonium chloride in an inert solvent. It is wellknown that the preferred solvents for this reaction are chlorinatedhydrocarbon solvents such as monochlorobenzene, tetrachloroethane,dichlorobenzene and the like. Preferably, the ammonium chloride ispresent in the hydrocarbon solvent in an amount of not more than 400 to500 grams per liter of solvent.

Large proportions of cyclic polymer are produced when a molar excess ofammonium chloride is maintained in the reaction mixture. When a highproportion of cyclic material is desired, the molar excess of ammoniumchloride is 10 to 25 mole percenLWhen the molar ratio of ammoniumchloride to phosphorus pentachloride is one to one, or less, largeamounts of linear polymer are formed. Acid-treated Montmorillonite claycatalyst catalyzes the formation of either high linear or high cyclicphosphonitrilic chlorides. Phosphorus pentachloride can be added to thereactions in many ways; however, it is usually added slowly as a 50 to60 percent solution in the solvent of choice in order to obtain a highproportion of cyclic polymers.

The acid-treated Montmorillonite clay catalyst is used in a proportionof at least 1 gram per mole of phosphorus pentachloride, and preferably3 to 15 grams per mole of phosphorus pentachloride. Larger amounts ofcatalyst, 50 grams or more per mole of phosphorus pentachloride can beused, but no appreciable advantages are obtained, and it is commerciallyundesirable to use such large amounts of catalyst.

The reaction of ammonium chloride with phosphorus pentachloride isgenerally run in the presence of an inert solvent. Solvents of choicehave boiling points within the desired temperature range for carryingout the reaction. The reaction may be run without the sol vent; however,handling of the reaction product is difficult. Halogenated solvents arepreferred for diluting the reaction mixture. Particularly preferred aremonochlorobenzene, dichlorobenzene and tetrachloroethane. Standardchemical processing equipment is used in the process of this invention.

The process of the present invention is carried out at an elevatedtemperature, preferably between about 100 C and the boiling point of thesolvent under the conditions of the reaction. It is often convenient,but not necessary to carry out the reaction at the boiling point of thesolvent under reflux. Temperatures of l C or above can be used, butthese high temperatures result in the formation of considerable amountsof polymeric phosphonitrilic chlorides. Preferably, the reaction iscarried out at temperatures between 125 and 160 C. A reactiontemperature substantially higher cyclic to linear polymers was measuredby the selective partitioning of the cyclic polymer into hexane. Theamount of reactants, the time required to feed the phosphoruspentachloride, the total reaction time, the

than 160 C is not favorable, since losses due to the dis- 5 ratio ofcatalyst to moles of phosphorus pentachloride, sociation of PCl to PCI;;and chlorine gas become sig-' the ercent of theor of hydro en chlorideas evolved I I e I u p y g g nlficant. The solvent of choice should boilsuffic1ently and the cyclic-linear ratio of the phosphonitrilic chlolowthat, when removed from the crude phosphonitrilic ride product e se t for th in Table]. V in TABLE I Grams Acid Mont- Total moril- Reacloniteof Moles of PCI:, tion per Theory Cyclic Reactants Fed. Time Mole HCILmear Ex. PC]; NH Cl Hrs. Hrs. PCl Off Ratio catalyst chloride roduct,undesirable polymerization does not EXAMPLE B HIGH-LINEAR POLYMER occur-25 A solution of 688 grams (5.0 moles) of phosphorus The Pf at which themacho" R 15 trichloride in 688 grams of monochlorobenzene was notCritical, 50 g mp m the desnjed placed in a 5-liter flask equipped witha stirrer, therrange 15 used, and the eilmlnatlon of y g Chlorldemometer, the chlorine inlet and a Dry Ice condensor. reactionby-products 1s not retarded. Most e- Chlorine gas was gradually added tothis solution (355 niently the reaction is carried out at atmosphericpres- 30 grams or 5.0 moles of chlorine) to make 1040 grams sure. Theaddition rate of phosphorus pentachloride (5.0 moles) of phosphoruspentachloride. The chlorine has a pronounced effect on the course of thereaction. a on Carried O in 90 minutes, ring Which Slow addition favorsthe formation of the cyclic polythe reaction temperature f if to 1 C duemers, whereas charging all of the phosphorus pentato the heatof theexotherm1c react1on. The pho sphorus chloride results in high yields ofan oily linear polymer pentachloride solution was 9 to Q to 60 andfraction. The reaction is continued until the evolution 2 3 gFZZE..,Z,ZL3IZZ1.3383 3%??? of hydrogen chloride gas has ceased. Thereact1on t1me (5 0 moles) of commercial ammonium chloride g i generallyvaries between about 6 9 about 25 hqurs' period of l5 minutes. Thereaction temperature was The followmg.examples further illustrate themven' raised to reflux over a period of about 1 hours, and thetlonproportlons f we'ght m the examples an d 4O reaction progress wasfollowed as in Example A. The throughout the spec1f1cat1on unlessotherwise 1nd1- reaction was completed in 21 hours with a recovery ofcated- 95% of the hydrogen chloride theoretically expected. EXAMPLE AHIGH CYCUC CONTE A control experiment using no catalyst was run; it Aseries of three runs using the Montmorillonite cata- :22: 2 3g2; f igggli ifi'g gzz gi fiyggg zg g g: lyst and a control using no catalyst wererun accordmg ride to the following procedure. The results are given inTable L As will be apparent to those skilled 1n the art, numer-Monochlombenzene 3,465 grams was added to a 22 ous modifications andvariations of the embodiments liter flask equipped with a stirrer,thermometer, jackettgg gg fi g zfigi i Sg a gi ifi gg g iigi mf gzed-addition funnel and a reflux condenser. To the claims P gmonochlorobenzene 1,624 grams (30.36 moles) technical commercialammonium chloride (50 to 200 What clamed mesh) and a catalytic amount ofacid-treated Montmoprocfiss for produfitlon of P P P rillonite clay wasadded. The level of catalyst used var- 55 Chlondes which conslstsessentially of f g P P ied from 80 to 300 grams on a dry weight basis.rustpelmgchlonde 'L ammomum .chlorlde having a to is: the gradual addmon9 51270 grams 9 moles), ence of at least 1 gram of acid-treatedMontmorillonite phosphorus pentachlorlde, as a solut1on 1n monoclay foreach grammole of PCIS charged to the reac chlorobenzene was begun. Therate of phosphorus pen- 60 tion mixtum tachloride introduction wasadjusted so that the addi- 2 The process of daim l in c o 1 gram of tionwas completed in about 20 hours. Introduction of phosphoruspentachloride to the control run required figg gzi g g figig g?ggggssfig pg f figgi are 27 ours.

The reaction rate was monitored y Rating the 3. The process of dam 1 1nWhlCh the react1on temevolved hydrogen chloride. The reaction mixturewas then filtered to remove the excess ammonium chloride and catalyst. Aportion of the filtrate was vacuum distilled to remove themonochlorobenzene. The ratio of perature is between and C.

4. The process of claim 1 in which the solvent is selected from thegroup consisting of monochlorobenzene, dichlorobenzene andtetrachloroethane.

* i i t

1. A PROCESS FOR THE PRODUCTION OF PHOSPHONITRILIC CHLORIDES WHICHCONSISTS ESSENTIALLY OF HEATING PHOSPHORUS PENTACHLORIDE WITH AMMONIUMCHLORIDE HAVING A PARTICLE SIZE GREATER THAN 200 MESH IN AN INERTSOLVENT AT A TEMPERATURE GREATER THAN 100*C AND IN THE PRESENCE OF ATLEAST 1 GRAM OF ACIDTREATED MONTMORILLONITE CLAY FOR EACH GRAM-MOLE OFPC15 CHARGED TO THE REACTION MIXTURE.
 2. The process of claim 1 in which3 to 15 grams of acid-treated Montmorillonite acid clay catalyst areused per gram-mole of phosphorus pentachloride.
 3. The process of claim1 in which the reaction temperature is between 125* and 180* C.
 4. Theprocess of claim 1 in which the solvent is selected from the groupconsisting of monochlorobenzene, dichlorobenzene and tetrachloroethane.